US President Donald Trump, a long-time critic of the JCPOA, faces a May 12 deadline to decide whether to pull out of the agreement. Trump has repeatedly warned that he might ultimately terminate the agreement reached under his predecessor Barack Obama.

He said on January 12 that he wanted America's European allies to use the 120-day period before sanctions relief again came up for renewal to agree to tougher measures and new conditions; otherwise Washington would pull out of the deal.

Under the multilateral nuclear agreement, Iran undertook to put limits on its nuclear program in exchange for the removal of nuclear-related sanctions imposed against Tehran.

Other parties to the agreement have all criticized the US president's hostile views, saying the deal is sound and has proven to be functioning.